Apparatus for magnetically deployable catheter with mosfet sensor and method for mapping and ablation

ABSTRACT

A mapping and ablation catheter is described. In one embodiment, the catheter includes a MOSFET sensor array that provides better fidelity of the signal measurements as well as data collection and reduces the error generated by spatial distribution of the isotropic and anisotropic wavefronts. In one embodiment, the system maps the change in potential in the vicinity of an activation wavefront. In one embodiment, the mapping system tracks the spread of excitation in the heart, with properties such as propagation velocity changes. In one embodiment, during measurement, the manifold carrying the sensor array expands from a closed position state to a deployable open state. Spatial variation of the electrical potential is captured by the system&#39;s ability to occupy the same three-dimensional coordinate set for repeated measurements of the desired site. In one embodiment, an interpolation algorithm tracks the electrogram data points to produce a map relative to the electrocardiogram data.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of application Ser. No.11/362,542, filed Feb. 23, 2006, titled “APPARATUS FOR MAGNETICALLYDEPLOYABLE CATHETER WITH MOSFET SENSOR AND METHOD FOR MAPPING ANDABLATION,” the disclosure of which is incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

A method and apparatus for navigating and recording electricalcharacteristics of the heart using a MOSFET sensor guided by amagnetically-deployable mechanism is described.

BACKGROUND

Cardiac mapping using catheters introduced precutaineously into theheart chambers while recording the electrical potential and subsequentlycorrelating the endocardial electrograms to specific anatomy of theheart suffers from multiple drawbacks. The use of fluoroscopy forcorrelating geometry and metrics is limited by the two-dimensionalimagery of the fluoroscopy. The geometrical interpolation of the dataand error reduction technique used in order to “best fit” the electrodeand the site is at best an approximation. Another drawback of theexisting art is the inability of existing methods to determine themeasurement position in order to collect additional data points.

Therefore, there is a substantial and unsatisfied need for an apparatusand method for guiding, steering, advancing, and locating the positionof the mapping electrode for measurement of electrical potential and forproviding a three-dimensional image data.

SUMMARY

These and other problems are solved by providing amagnetically-deployable catheter control and system using a MOSFETsensor array. In one embodiment, the sensor provides better fidelity ofthe signal measurements as well as data collection and reduces the errorgenerated by spatial distribution of the isotropic and anisotropicwavefronts. In one embodiment, the system maps the change in potentialin the vicinity of the activation wavefront, which provides data on thethickness of the activation wavefront. In one embodiment, the mappingsystem tracks the spread of excitation in the heart, with propertiessuch as propagation velocity changes. In one embodiment, duringmeasurement, the manifold carrying the sensor array expands from aclosed position state to a deployable open state [umbrella], which cansample and hold a set of data points for each QRS cycle. Spatialvariation of the electrical potential is captured by the system'sability to occupy the same three-dimensional coordinate set for repeatedmeasurements of the desired site. In one embodiment, an interpolationalgorithm tracks the electrogram data points so as to produce a maprelative to the electrocardiogram data.

In one embodiment, a magnetically-deployable catheter uses a MOSFETsensor matrix for mapping and ablation. In one embodiment, a MOSFETsensor array and RF radiating antennas are configured to providemultiple states of deployable sensor configurations (radial). In oneembodiment, radial umbrella-like arrays are used. The arrays senseactivation spread as an energetic event. The dynamic variations ofelectric potential during de-polarization and re-polarization of theexcitable cells of the heart can be measured as the activationavalanches.

In one embodiment, the electrical and magnetic fields during cellactivation, are measured. In one embodiment, an algorithm describesthese fields and calculates the dynamic spread of the energy containedin the electric and magnetic fields, and in the multi-source excitablecell of the hearts myocardium region.

The energy event as a methodology of representing the cardiac activationspread can be used for diagnostic and pathological assessment as well asfor forming maps of the superimposed electric and energy wave upon theanatomical detail generated by x-ray imagery or other imaging methods(e.g., MRI, CAT scans, etc.).

In one embodiment, a magnetically-deployable catheter with MOSFET sensorcontrolled by a magnetic catheter guidance, control, and imagingapparatus as described in U.S. patent application Ser. No. 10/690,472titled, “System and Method for Radar Assisted catheter Guidance andControl” and US Patent 2004/0019447 and provisional application No.60/396,302, the entire contents of which are hereby incorporated byreference.

In one embodiment, the system provides ablation and mapping whilenavigating and controlling the movements of the sensors and antennasmanually.

In one embodiment, the system provides electrocardiographic maps of themyocardium region.

In one embodiment, the ablation and mapping apparatus ismagnetically-deployable using mechanism which provides the measurementof surface potential and activation time matrix by the use of aplurality of sensing points. This measurement is further refined (ErrorReduction Technique) along one or more measurement radii change indesired increments, and further enhanced by measurement steps along thecircumference for each radius.

The electric potential data table provides for at least 24 element pairs(E_(n) and t_(n)) for each catheter position along the myocardium.

In one embodiment, the sensor head measures the conductivity matrixbetween the sensing points during activation. The measurement can berefined (Error Reduction Technique) along radii changed in desiredincrements. In one embodiment, the measurements fidelity is improved byrotating the measurements as a sequence of measurements around thecircumference for each radius. The conductivity data table has multipleelements for each new catheter position along the myocardium.

In one embodiment, the mapping capabilities of electric potential andconductivity activation spread measurements is supplemented with adisplay of the magnitude and direction of the activation energy wavealong the myocardium. This energy wave contains complimentaryinformation to the electric field measurements about the anisotropy ofthe myocardium related to its conductivity during the activationexcitation spread.

In one embodiment, the apparatus displays the directional anisotropybetween the electric field and the conductivity vector for cardiacdisorder or pathology correlation.

In one embodiment, the system includes an RF ablation tool. The RFablation antennas can be selected and activated independently byconfiguring the driving RF (300 kHz to 1 MHZ) voltage phase-angle toobtain the required lesion geometry, such as, for example, elongatedlinear cuts with desired ablation depth.

In one embodiment, the ablation and mapping catheter uses the radarimaging and fiduciary marker technique identified by U.S. applicationSer. No. 10/690,472, hereby incorporated by reference, for use bycatheter fitted with magnetically coupled devices.

In one embodiment, the collected potential, timing, conductivity andenergy wave data is interpolated between the sensors and extrapolatedinto the muscle tissues of the heart. The results are then overlaid anddisplayed together with the apparatus noted by application Ser. No.10/690,472 or other imaging systems.

In one embodiment, the catheter guidance system includes a closed-loopservo feedback system. In one embodiment, a radar system is used todetermine the location of the distal end of the catheter inside thebody, thus, minimizing or eliminating the use of ionizing radiation suchas X-rays. The catheter guidance system can also be used in combinationwith an X-ray system (or other imaging systems) to provide additionalimagery to the operator. The magnetic system used in the magneticcatheter guidance system can also be used to locate the catheter tip toprovide location feedback to the operator and the control system. In oneembodiment, a magnetic field source is used to create a magnetic fieldof sufficient strength and orientation to move a magnetically-responsivecatheter tip in a desired direction by a desired amount.

In one embodiment, a multi-coil cluster is configured to move and/orshape the location of a magnetic field in 3D space relative to thepatient. This magnetic shape control function provides efficient fieldshaping to produce desired magnetic fields for catheter manipulations inthe operating region (effective space).

One embodiment includes a catheter and a guidance and control apparatusthat allows the surgeon/operator to position the catheter tip inside apatient's body. The catheter guidance and control apparatus can maintainthe catheter tip in the correct position.

One embodiment includes a catheter and a guidance and control apparatusthat can steer the distal end of the catheter through arteries andforcefully advance it through plaque or other obstructions.

One embodiment includes a catheter guidance and control apparatus thatis more intuitive and simpler to use, that displays the catheter tiplocation in three dimensions, that applies force at the catheter tip topull, push, turn, or hold the tip as desired, and that is configured toproducing a vibratory or pulsating motion of the tip with adjustablefrequency and amplitude to aid in advancing the tip through plaque orother obstructions. One embodiment provides tactile feedback at theoperator control to indicate an obstruction encountered by the tip.

In one embodiment, the Catheter Guidance Control and Imaging (CGCI)system allows a surgeon to advance, position a catheter, and to view thecatheter's position in three dimensions by using a radar system tolocate the distal end of the catheter. In one embodiment, the radar datacan be combined with X-ray or other imagery to produce a compositedisplay that includes radar and image data. In one embodiment, the radarsystem includes a Synthetic Aperture Radar (SAR). In one embodiment, theradar system includes a wideband radar. In one embodiment, the radarsystem includes an impulse radar.

One embodiment includes a user input device called a “virtual tip.” Thevirtual tip includes a physical assembly, similar to a joystick, whichis manipulated by the surgeon/operator and delivers tactile feedback tothe surgeon in the appropriate axis or axes if the actual tip encountersan obstacle. The Virtual tip includes a joystick type device that allowsthe surgeon to guide the actual catheter tip through the patient's body.When the actual catheter tip encounters an obstacle, the virtual tipprovides tactile force feedback to the surgeon to indicate the presenceof the obstacle. In one embodiment, the joystick includes a PHANTOM®Desktop™ haptic device manufactured by Sensable Technologies, Inc. Inone embodiment, the virtual tip includes rotary control systems such asthose manufactured by Hitachi Medical Systems America, Inc.

In one embodiment, the physical catheter tip (the distal end of thecatheter) includes a permanent magnet that responds to the magneticfield generated externally to the patient's body. The external magneticfield pulls, pushes, turns, and holds the tip in the desired position.One of ordinary skill in the art will recognize that the permanentmagnet can be replaced or augmented by an electromagnet.

In one embodiment, the physical catheter tip (the distal end of thecatheter) includes a permanent magnet and two or more piezoelectricrings, or semiconductor polymer rings to allow the radar system todetect the second harmonics of the resonating signal emanating from therings.

In one embodiment, the CGCI apparatus provides synchronization by usinga radar and one or more fiduciary markers to provide a stereotacticframe of reference.

In one embodiment, the CGCI apparatus uses numerical transformations tocompute currents to be provided to various electromagnets and positionof one or more of the electromagnet to control the magnetic field usedto push/pull and rotate the catheter tip in an efficient manner.

In one embodiment, the CGCI apparatus includes a motorized and/orhydraulic mechanism to allow the electromagnet poles to be moved to aposition and orientation that reduces the power requirements desired topush, pull, and rotate the catheter tip.

In one embodiment, the CGCI apparatus is used to perform an implantationof a pacemaker during an electrophysiological (EP) procedure.

In one embodiment, the CGCI apparatus uses radar or other sensors tomeasure, report and identify the location of a moving organ within thebody (e.g., the heart, lungs, etc.) with respect to the catheter tip andone or more fiduciary markers, so as to provide guidance, control, andimaging to compensate for movement of the organ, thereby, simplifyingthe surgeon's task of manipulating the catheter through the body.

In one embodiment, a servo system has a correction input thatcompensates for the dynamic position of a body part, or organ, such asthe heart, thereby, offsetting the response such that the actual tipmoves substantially in unison with the dynamic position (e.g., with thebeating heart).

In one embodiment of the catheter guidance system: i) the operatoradjusts the physical position of the virtual tip, ii) a change in thevirtual tip position is encoded and provided along with data from aradar system, iii) the control system generates servo system commandsthat are sent to a servo system control apparatus, iv) the servo systemcontrol apparatus operates the servo mechanisms to adjust the positionof one or more electromagnet clusters by varying the distance and/orangle of the electromagnet clusters and energizing the electromagnets tocontrol the magnetic catheter tip within the patient's body, v) the newposition of the actual catheter tip is then sensed by the radar,thereby, allowing synchronization and superimposing of the catheterposition on an image produced by fluoroscopy and/or other imagingmodality, vi) providing feedback to the servo system control apparatusand to the operator interface, and vii) updating the displayed image ofthe catheter tip position in relation to the patient's internal bodystructures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a system block diagram for a surgery system that includes anoperator interface, a catheter guidance system (CGCI) and surgicalequipment including a system for mapping and ablation apparatus.

FIG. 1A is a block diagram of the imaging module for use in the CGCIsurgery procedure that includes the catheter guidance system, a radarsystem, Hall Effect sensors and the mapping and ablation apparatus.

FIG. 1B is a flow chart of the process for conducting an ablationprocedure using the CGCI system that includes a radar system, HallEffect sensors and the mapping and ablation apparatus.

FIG. 2 is a block diagram of the mapping and ablation control andmapping system.

FIG. 3 shows computer-generated and E-cardiac images including: an ECGgraph with its corresponding ECG plot on an x-y plane; a conductivitymap represented on the x-y plane; and a composite energy and E-vectordisplay.

FIG. 3A is a flow chart of the pre-ablation simulation used to predictthe ablation results prior to performing the actual ablation procedure.

FIGS. 4, 4A, 4B and 4C shows an orthographic representation of themapping and ablation catheter with its physical attributes.

FIGS. 4D, 4E, 4F, and 4G are orthographic depictions of amagnetically-deployable guidewire and ablation tool and catheter.

FIG. 4H shows an orthographic representation of the mapping and ablationcatheter in a deployed state.

FIGS. 4I, 4J, 4K, 4L, and 4M are orthographic depictions of the wiringand electrical connections of the antennas, MOSFETs, and coils formingthe circuit layout of the ablation and mapping assembly.

FIG. 5 is a schematic diagram of the MOSFET sensor used in measuring theelectric potential.

FIGS. 6, 6A, and 6B show the magnetically-deployable mechanism used toreduce the measurement error and increase the surface area of themeasured event.

FIG. 7 is a cross-sectional view of the RF antenna.

FIG. 8 is a schematic representation of the ablation tool and itsattributes.

FIGS. 9 and 9A show the catheter with closed, intermediary and fullyopen geometry states.

FIG. 9B shows the endocardial electrogram map resulting from sequentialmeasurements of electrical potential detected by the catheter at variousopen geometry states.

FIG. 10 is an isometric drawing of the image capture and maps formation.

FIG. 11 is a block diagram of the radar used in forming the dimensionalmanifold of the electrogram.

FIGS. 11A and 11B illustrate identification of the catheter position andthe anatomical features.

FIGS. 12 and 12A show the manifold with its fiduciary markers used informing the stereotactic frame.

DETAILED DESCRIPTION

FIG. 1 is a system block diagram for a surgery system 800 that includesan operator interface 500, a CGCI system 1500, the surgical equipment502 (e.g., a catheter tip 2, etc.), one or more user input devices 900,and a patient 390. The user input devices 900 can include one or more ofa joystick, a mouse, a keyboard, a virtual tip 905, and other devices toallow the surgeon to provide command inputs to control the motion andorientation of the catheter tip 2.

In one embodiment, the CGCI system 800 includes a controller 501 and animaging synchronization module 701. FIG. 1 shows the overallrelationship between the various functional units and the operatorinterface 500, auxiliary equipment 502, and the patient 390. In oneembodiment, the CGCI system controller 501 calculates the Actual Tip(AT) position of the distal end of a catheter. Using data from theVirtual Tip (VT) 905 and the imaging and synchronization module 701, theCGCI system controller 501 determines the position error, which is thedifference between the actual tip position (AP) and the desired tipposition (DP). In one embodiment, the controller 501 controlselectromagnets to move the catheter tip in a direction selected tominimize the position error (PE). In one embodiment, the CGCI systemcontroller 501, provides tactile feedback to the operator by providingforce-feedback to the VT 905.

FIG. 1A is a block diagram of a surgery system 503 that represents oneembodiment of the CGCI system 1500. The system 503 includes thecontroller 501, a radar system 1000, a Hall effect sensor array 350 anda hydraulically-actuated system 1600. In one embodiment, the sensor 350includes one or more Hall effect magnetic sensors. The radar system 1000can be configured as an ultra-wideband radar, an impulse radar, aContinuous-Wave (CW) radar, a Frequency-Modulated CW (FM-CW) radar, apulse-Doppler radar, etc. In one embodiment, the radar system 1000 usesSynthetic Aperture Radar (SAR) processing to produce a radar image.

In one embodiment, the radar system 1000 includes an ultra-widebandradar such as described, for example, in U.S. Pat. No. 5,774,091, herebyincorporated by reference in its entirety. In one embodiment, the radar1000 is configured as a radar range finder to identify the location ofthe catheter tip 2. The radar 1000 is configured to locate referencemarkers (fiduciary markers) placed on or in the patient 390. Dataregarding location of the reference markers can be used, for example,for image capture synchronization 701. The motorized hydraulically andactuated motion control system 1600 allows the electromagnets of thecylindrical coils 51AT and 51DT to be moved relative to the patient 390.

In one embodiment, the use of the radar system 1000 for identifying theposition of the catheter tip 2 has advantages over the use ofFluoroscopy, Ultrasound, Magnetostrictive sensors, or SQUID. Radar canprovide accurate dynamic position information, which provides forreal-time, relatively high resolution, relatively high fidelitycompatibility in the presence of strong magnetic fields.Self-calibration of the range measurement can be based on time-of-flightand/or Doppler processing. Radar further provides for measurement ofcatheter position while ignoring “Hard” surfaces such as a rib cage,bone structure, etc., as these do not substantially interfere withmeasurement or hamper accuracy of the measurement. In addition, movementand displacement of organs (e.g., pulmonary expansion and rib cagedisplacement as well as cardio output during diastole or systole) do notrequire an adjustment or correction of the radar signal. Radar can beused in the presence of movement since radar burst emission above 1 GHzcan be used with sampling rates of 50 Hz or more, while heart movementand catheter dynamics typically occur at 0.1 Hz to 2 Hz.

In one embodiment, the use of the radar system 1000 reduces the need forcomplex image capture techniques normally associated with expensivemodalities such as fluoroscopy, ultrasound, Magnetostrictive technology,or SQUID which require computationally-intensive processing in order totranslate the pictorial view and reduce it to a coordinate data set.Position data synchronization of the catheter tip 2 and the organ inmotion is available through the use of the radar system 1000. The radarsystem 1000 can be used with phased-array or Synthetic Apertureprocessing to develop detailed images of the catheter location in thebody and the structures of the body. In one embodiment, the radar system1000 includes an Ultra Wide Band (UWB) radar with a relatively highresolution swept range gate. In one embodiment, a differential samplingreceiver is used to effectively reduce ringing and other aberrationsincluded in the receiver by the near proximity of the transmit antenna.As with X-ray systems, the radar system 1000 can detect the presence ofobstacles or objects located behind barriers such as bone structures.The presence of different substances with different dielectric constantssuch as fat tissue, muscle tissue, water, etc., can be detected anddiscerned. The outputs from the radar can be correlated with similarunits such as multiple catheters used in Electro-Physiology (EP) studieswhile detecting spatial location of other catheters present in the heartlumen. The radar system 1000 can use a phased array antenna and/or SARto produce 3D synthetic radar images of the body structures, cathetertip 2, organs, etc.

In one embodiment, the location of the patient relative to the CGCIsystem (including the radar system 1000) can be determined by using theradar 1000 to locate one or more fiduciary markers. In one embodiment,the data from the radar 1000 is used to locate the body with respect toan imaging system. The catheter position data from the radar 1000 can besuperimposed (synchronized) with the images produced by the imagingsystem. The ability of the radar and the optional Hall effect sensors350 to accurately measure the position of the catheter tip 2 relative tothe stereotactic frame allows the controller 501 to control movement ofthe catheter tip.

FIG. 2 is a functional block diagram of the magnetically-deployableelectrocardiographic (ECG) and RF ablation catheter (MDAMC) and itsassociated supporting equipments. The system 1600 includes a catheterassembly, having an electrocardiographic and ablation tool. An ECGsensor head 100 includes eight MOSFET sensors 7 (S₁, S₂, S₃, S₄, S₅, S₆,S₇, S₈) and eight RF antennas 8, a coil 3, and its counterpart coil 14(forming the magnetic mechanism), an elongated catheter body having aproximal end and an internal longitudinal lumen 1, and a bus wireharness 15. The tool is connected via the bus wire 15 to the ECG coils 3and 14 driver and control 204. The electrocardiographic mapping andablation catheter is provided to an ECG data interpolation unit 205.Data analyzed by the ECG interpolation unit 205 is used by the ablationRF power generator 94 which activates the RF antennas 8. The informationgenerated by the ECG probe is provided to the application specificcomputer 91 with its software 200 made by National Instrument andMathLab processing software used to control the probe to display itsfindings on the control display 93, as well as the electrocardiacdisplay 92. The system is powered by a UPS 90.

In one embodiment, a diagnostic method employed by the magneticallydeployable mapping and ablation catheter (MDAMC) is statistically basedon correlating electrical activity with anatomical features whichfurther allows the practitioner to evaluate certain patterns. In oneembodiment, a biophysical model is used with the electrophysiologicaloutputs to cardiac function as well as to the waveform obtained to forma map or maps of the cardiac wave. The data points measured by thesensor 100 with its MOSFET devices 7 coupled with the wavefrontcharacterization as defined by the Poynting Energy Vector (PEV) 49, areanalyzed and graphically represented using the control display 93 andthe e-cardiac display 92. Correlating the electric generator during thedepolarization phase in the cardiac model is related to the fact thatsurface-carrying elementary current dipoles (from the cellular ionkinetics across membranes) imply the subsequent avalanche (wavefronts)as it progresses through the myocardium (see e.g., A. Van OOsterom“Source Modeling of Bioelectric Signals”, Proc. 3-ed, Rayner GranitSymposium (J. Malmivno ed.) Vol. 8-6, pp 27-32 1994).

FIG. 1B is a flow chart of the process for conducting an ablationprocedure using the CGCI system that includes a radar system, HallEffect sensors and the mapping and ablation apparatus. In oneembodiment, the catheter is navigated to the mapping site using the CGCIand the Synthetic Aperture Radar. The catheter sensor arms are openedand touch the cardiac tissue. The radar reads the site position, and thesensor arm diameter and angle setting is recorded. The sensors thenautocalibrate and measure the activation potential and impedances. Theresults are placed into the matrix created for activation potential andthe matrix created for impedances; the results are accumulated over manycycles. The diameter and angle of the catheter is detected and then bothare increased electromagnetically, and new data matrixes are recorded atthe new diameter and angle. The activation potential and impedancematrix data is scaled and loaded into a high speed Spice computationalprogram. The trigger threshold, timing cycle and interconnectingimpedances of the simulated excitable cells are correlated and set torepresent the tissue property at the site. These values are modified bythe data. The output of the Spice simulation of the E vector map, theimpedance map, and the Energy map are displayed as 2D/3D surfaces,vectors and repetitive transient wavefronts. Then the user marks a triallesion area. Then the system displays the effects of the pre-ablationsimulation of the trial lesion.

FIG. 2 is a functional diagram of the main attributes which will becomeclear for those familiar with the art as will reading the descriptionsand ensuing objects noted by the drawings which accompany them.

FIG. 3 shows the wavefront showing the Poynting Energy Vector (PEV) 49measuring the electrical potential and interpretation of the electricalactivity as well as mapping of such wavefront propagation. In oneembodiment, a mathematical algorithm is used for interpolation so as toachieve a relatively coherent view of the activation path while derivinga set of secondary measurable values such as Electric Heart Vector(EHV), Magnetic Dipole (MHV) as well as impedance measure of themyocardium wall.

The first assumption this method used is that cardiac activation spreadis a relatively energetic event. It is further assumed in this modelthat in addition to the dynamic variations of electrical potentialsduring de-polarization and re-polarization of the excitable cell of theheart, a spread of electro magnetic energy is observed as the activationavalanches.

In one embodiment, the system measures both the electric and magneticfields during cell activation, (model relationship of normal activationsequences and degree of inter individual variability is detailed, forexample, in K. Simelius et al, “Electromagnetic Extra cardiac fieldssimulated with bidomain propagation model,” Lab of BiomedicalEngineering, Fin-02015, Hut, Finland, hereby incorporated by reference).

The dynamic spread of the energy contained in the electric and magneticfields are then described by the use of Maxwell equations as applied tothe conduction system of the individual rather than reproducing theanatomical variation that leads to anisotropic myocardium. This “energymodel” approach provides for calculation of the dynamic spread of energycontained in the electric and magnetic fields and respectively in themultisource excitable cells of the heart's myocardium region to berepresented and hence mapped without the assumptions of idealizedmodels.

The data analysis and extraction of diagnostic as well as pathologicalinformation can be mapped as a superimposed electric and energy wave.

To overcome the measurement limitations of myocardial anisotropy, anddue to production of slam magnetic fields during an activation sequence,the algorithm and apparatus is able to regain the detection capabilityof a magnetic dipole (MHV) by the use of another vector derived fromMaxwell's equations, the Poynting Energy Vector (PEV) 49.

Clinical observations reported that measuring the angle between vectorsof equivalent electric dipole (electric heart vector, EHV) and magneticdipole (Magnetic Heart Vector) provides significant corollaryinformation about the myocardium conductivity. The overall anisotropiccase of the myocardium conductivity is represented by a tensor. Thedegree of anisotropic conductivity manifestation is characterized by anangle along the transversal and axial conductivity paths.

The solution for measuring and deriving the relationship between theElectric Heart Vector (EHV) and its respective magnetic dipole vector(MHV), (hence, supplementing the analytical mapping with additionalinformation about the myocardium conductivity and anistrophy), isderived from Maxwell's equation as the Poynting Energy Vector (PEV) 49.The PEV is constructed from the multiple potential and impedance vectorsof the measurements. In one embodiment, a magnetically-deployablemapping and ablation catheter using MOSFET is used for potentialsensing. A matrix arrangement for phase rotation for RF generation andthe angle β between the PEV and EHV is used to infer the features ofanisotropy in the myocardium. The anisotropy of the conductivity isuniform, hence activation energy change generated and consumed by theionic diffusion process is within the activation region of themeasurement. Thus, the volume integrations is accurate, with a margin oferror reduction based on two independent techniques, one statistical(monte carlo) and Tikhonov regularization filtering.

In one embodiment, the law of energy conservation is used for the timeperiod of the two QRS cycle (e.g., 1152 data measurements) to acquirethe initial baseline data foundation to form the map.

The validity of the Poynting Energy Vector (PEV) 49 derivation iscorroborated by the fact that the activation spread obeys themathematical identity that the Poynting Energy Vector (PEV) 49 isdirectly exhibiting the E and B fields phase angle relationship. Theintegral form of Maxwell's equations leads to the Poynting Energy Vector(PEV) 49, and to the substitution of E and Z derivations of this vector.

Maxwell's second set of time varying equations can be written as:

$\begin{matrix}{{\nabla{\times E}} = {- \frac{B}{t}}} & (1)\end{matrix}$

and

$\begin{matrix}{{\nabla{\times B}} = {{{ϛ\mu}\frac{E}{t}} + {\mu \; J}}} & (2)\end{matrix}$

By multiplying B and E respectively and subtracting Equation (2) fromEquation (1) and using vector identities yields

$\begin{matrix}{{B \cdot ( {\nabla{\times E}} )} = {{- B} \cdot \frac{B}{t}}} & (3)\end{matrix}$

and

$\begin{matrix}{{E \cdot ( {\nabla{\times B}} )} = {{{ϛ\mu}( {E \cdot \frac{E}{t}} )} + {\mu ( {E \cdot J} )}}} & (4)\end{matrix}$

Subtracting, rearranging and using vector identities yields.

$\begin{matrix}{{\nabla{\cdot ( {E \times B} )}} = {{B \cdot ( {\nabla{\times E}} )} - {E \cdot ( {\nabla{\times B}} )}}} & (5) \\{{\nabla~{\cdot ( {E \times B} )}} = {{{- \frac{\;}{x}}( {\frac{1}{2}{B \cdot B}} )} - {\frac{}{x}( {{ϛ\mu}\; {E \cdot E}} )} - {\mu \; {JE}}}} & (6) \\{{{\nabla{\cdot \lbrack ( {\frac{1}{\mu}E \times B} ) \rbrack}} + {\frac{\;}{x}\lbrack {{\frac{ϛ}{2}E^{2}} + {\frac{1}{2\mu}B^{2}}} \rbrack} + {J \cdot E}} = 0} & (7)\end{matrix}$

Integrating both sides of Equation (7) over the volume V and within theboundary Y gives:

$\begin{matrix}\text{?} & \; \\{{{{\int_{Y}^{\;}{\frac{1}{\mu}{( {E \times B} ) \cdot \ {S}}}} + {\frac{\;}{x}{\int_{V}{( {{\frac{ϛ}{2}E^{2}} + {\frac{1}{2\mu}B^{2}}} )\ {\tau}}}} + {\int_{V}^{\;}{( {{J \cdot E} - {\sigma \; E^{2}}} )\ {\tau}}}} = 0}{\text{?}\text{indicates text missing or illegible when filed}}} & (8)\end{matrix}$

Equation (8) is a representation of the energy equation in which thefirst term (8.1) is the energy flux out of Y boundary of V. The secondterm (8.2) is the rate of change of the sum of the electric and magneticfields. The third term (8.3) is the rate of work within V done by thefields on the ionic charges.

The last term in Equation (8) assumes the inclusion of the energy of themultiple sources of cell, ionic charge exchanges, thus:

$\begin{matrix}{{{\int_{Y}^{\;}{\frac{1}{\mu}{( {E \times B} ) \cdot \ {S}}}} + {\frac{\;}{x}{\int_{V}{( {{\frac{ϛ}{2}E^{2}} + {\frac{1}{2\mu}B^{2}}} )\ {\tau}}}} + {\int_{V}^{\;}{( {{J\; \bullet \; E} - {\sigma \; E^{2}}} )\ {\tau}}}} = 0} & (9)\end{matrix}$

Equation (9) leads to the Poynting Energy Vector (PEV) 49 of

$\begin{matrix}{{E = {{\frac{1}{\mu}( {E \times B} )} + s}}{{{where}\mspace{14mu} {\nabla\bullet}\; s} = {0\mspace{14mu} ( {{Poynting}\mspace{14mu} {Energy}\mspace{14mu} {Vector}} )}}} & (10)\end{matrix}$

The parameter of interest is the angle between the electric field andenergy field. The vector E is obtained from energy vector from E fieldmeasurements by calculating the Z impedance vector.

By using the measured potentials V_(m) and by employing Poissonequation, the E electric field is obtained:

∇□σ·∇V _(m)=0 and E=−∇□V _(m)  (11)

Then, the Poynting Energy Vector (PEV) 49 can be written:

$\begin{matrix}{E = {\frac{1}{\mu}( {{( {E\; \bullet \; E} ) \cdot \frac{1}{Z}} + c} )\overset{\_}{n}}} & (12)\end{matrix}$

Where the E vector and impedance Z can be calculated from the measureddata points.

One can further calculate the angle β between the E field and E energyvector, where the difference is such that:

90° −α=β.  (13)

A display of the E energy vector is useful for cardiac disorderidentification. The E potential display serves a similar purpose as withother ECG systems, and the Z conductivity display is used to calculatethe RF ablation power setting prior to the ablation procedure. FIG. 3Ais a flow chart showing use of the pre-ablation simulation to verify theablation results prior to performing the ablation procedure. In oneembodiment, measurements 3000 of E energy data and Z conductivity dataare collected from the electrocardiographic mapping and ablationcatheter 600. This data is processed and displayed on a control display93 and/or e-cardiac display 92. The user can mark a trial ablation area3001 to conduct a simulation to verify the ablation results prior toperforming the lesion. After the user marks the trial ablation area3001, the system recalculates the E energy vector and Z conductivity toaccount for the hypothetical lesion, and determines the amount of RFenergy that is necessary to create the lesion such that the desiredconduction path is severed. Then the system displays the information3002 on control display 93 and e-cardiac display 92. After analyzing theinformation, the user makes a decision 3003 as whether the user desiresto repeat the process or conduct the ablation procedure based on thesimulation.

The Poynting Energy Vector (PEV) 49 indicates that there is a flux ofenergy where E and B are simultaneously present. The spread of theenergy flux in the case of Maxwell's derivation is further defined bythe wave equation:

$\begin{matrix}{{\nabla{\times E}} = {- \frac{B}{t}}} & (14)\end{matrix}$

taking the curl of each side

$\begin{matrix}{{\nabla{\times {\nabla{\times E}}}} = {{- \frac{\;}{x}}( {\nabla{\times B}} )}} & (15)\end{matrix}$

then

$\begin{matrix}{{{\nabla( {\nabla{\cdot E}} )} - {\nabla^{2}E}} = {{- \frac{\;}{x}}( {{ϛ\mu}\frac{E}{t}} )}} & (16)\end{matrix}$

Hence

$\begin{matrix}{{{\nabla^{2}E} - {{ϛ\mu}\frac{\partial^{2}E}{\partial t^{2}}}} = 0} & (17)\end{matrix}$

which is the wave equation.

In one embodiment, a simplified FEA program is used to extrapolate theenergy wave for display.

The conditions for defining the actual material constants çμ and themeasured Z are related to Hadamord observation for a well posed problemso as to yield a solution for each data set.

FIG. 3 is a computer generated 91 and E-cardiac displayed 92 imagecomprising of 4 basic visual; an ECG graph 54 with its corresponding ECGplot and an x-y plane; a conductivity map represented on the x-y planeand a composite energy and E-vector display 53.1. The visual shown inFIG. 3 is the result of the observation that cardiac activation spreadis an energetic event as defined by the formalism presented. Theapparatus 1600 measure the cardiac activation spreads as an energeticevent (using the MOSFET Sensor Head 100). The dynamic variations ofelectric potentials during de-polarization and re polarization of theexcitable cells is measured, computed, and displayed as a spread ofelectromagnetic energy (as an activation avalanches). This energy isgenerated by the myriads of excitable cells and expands within the heartby propagating as an energy wavefront described by the formalism inEquation (17).

This wavefront propagation provides the clinician addition diagnosticinformation in addition to the prior art ECG measurements. Deducing themagnetic heart vector (MHV) by using, at least in part, the energy heartvector PEV 49 is facilitated by the fact that the CGCI navigating andcombining apparatus 501. By using the measured conductivity value andthe corresponding ECG data, it is possible to derive the PEV 49 valuewhich represent the energy heart vector (EHV), were E and Z issubstituted for B. The apparatus 1600 measures and constructs the energyvector from the multiple potential and impedance vectors of themeasurements and the algorithm for computing the PEV 49 and the EHV. Thecomputer 91 and its software 200 such as, for example, Labview andMathLab, can calculate and display the composite image of the energyvector 49 and the E-vector 40 shown as an image 53.1. From the anglebetween the PEV 49 and the EHV 40, the physician can infer the featuresof anisotropy in the myocardium. In summary, FIG. 3 shows theelectrocardigraphic maps of the myocardium region with details ofdirectly measured potentials on the endocardial surface. It furthermeasures the surface potential and activation time matrix. The apparatus1600 measures the conductivity-time matrix between the sensing pointsduring activation. The composite display indicates the directionalanisotropy between the sensing points during activation. The compositedisplay shows the directional anisotropy between the electric potentialvector and the energy vector for the cardiac disorder.

FIGS. 4, 4A, 4B, 4C and 4H are orthographic representations of themagnetically-deployable ablation and mapping catheter 600. An elongatedcatheter 1 body having a proximal end and an internal longitudinaldistal end lumen. The catheter 1 is coupled to permanent magnet 2,forming part of the dynamic mechanism of the deployable sensor headassembly 50. The magnetically-deployable sensor head 50, includes aflange holder 5, which supports the semispherical dome 9, protecting theeight sensors 7, and their associated RF antennas 8, in a cluster asshown. The sensor head 50 extends towards catheter 1 body to formcylinder 9A which is received into a cavity 3 that is within thepermanent magnet 2. The interior of cylinder 9A contains one or morespiral ridges 9B for engaging a screw, bolt or other device withcorresponding spiral ridges. In one embodiment, arms 6 connect to aplurality of springs which connect to the deployable sensor head 50 suchthat the deployable sensor head 50 is in the closed state when thesprings are relaxed. When the axial movement of coils 3 and 14 displacesthe arm 6 (which holds the sensors 7 and the RF antenna 8) so as to forman “umbrella” with multiple deployment states (201, 202, and 203), theplurality of springs provide resistance to bias the arms 6 towards tothe closed position. In one embodiment, arms 6 connect to a cable thatallows the user to mechanically open and close the deployable sensorhead 50 without the use of axial movement of coils 3 and 14.

Two coils 3 and 14 are shown as traveling on a guide rail 4. Theassembly is further fitted with an irrigation tunnel 10, and a coolingmanifold (not shown for clarity). The catheter 600 is further embeddedwith a conductive ring 13, forming the ground of the electrical circuitof the ablation and potential measurements (a feature which becomesclearer in the ensuing Figures).

FIG. 4A depicts the sensor head assembly 50, in its closed state wherethe antennas 8, are nested in the semispherical dome 9 and its functionis explained in detail while comparing the intermediary state 202 andfully deployable state (the umbrella) shown in FIG. 4C. Therelationships between the three deployable states; 201 closed, 202intermediary and fully deployable state 203 in connection with theMOSFET sensor 7 measurements and the RF antenna 8 radiating mode aredescribed.

The configuration shown in FIG. 4 where the irrigation tunnel is leadingto the irrigation manifold 10, is used to provide a saline watersolution so as to cool the radiating antennas 8, while improving theconductivity measurements 62 (impedance (Z)) during the ablationprocedure.

FIG. 4B further shows the use of a guidewire 379, inserted through thetunnel cavity 10 (used for irrigation) so as to afford a safety measureto allow the catheter head 50 to be retrieved back to its closed state201. In one embodiment, guidewire 379 screws into region 9B to connectto cylinder 9A. The safety procedure is such that when a power failureor debris collecting on the catheter (such as fat tissue, plaque, or acombination thereof) surfaces prevents retrieval of the antennas 8 toits closed state 201. The operator then inserts a guidewire 379 throughthe irrigation tunnel, engages cylinder 9A, and mechanically pulls theflange 5 back to its closed state.

FIGS. 4D and 4E show an improved catheter assembly 375 and guidewireassembly 379 to be used with the CGCI apparatus 1500. The catheterassembly 375 is a tubular tool that includes a catheter body 376 whichextends into a flexible section 378 that possesses increased flexibilityfor allowing a more rigid responsive tip 2 to be accurately steeredthrough a torturous path.

The magnetic catheter assembly 375 in combination with the CGCIapparatus 1500 reduces or eliminates the need for the plethora of shapesnormally needed to perform diagnostic and therapeutic procedures. Thisis due to the fact that during a conventional catheterization procedure,the surgeon often encounters difficulty in guiding the conventionalcatheter to the desired position, since the process is manual and relieson manual dexterity to maneuver the catheter through a tortuous path of,for example, the cardiovascular system. Thus, a plethora of catheters invarying sizes and shapes are to be made available to the surgeon inorder to assist him/her in the task, since such tasks require differentbends in different situations due to natural anatomical variationswithin and between patients.

By using the CGCI apparatus 1500, only a single catheter is needed formost, if not all patients, because the catheterization procedure can beachieved with the help of an electromechanical system that guides themagnetic catheter and guidewire assembly 379 to the desired positionwithin the patient's body 390 as dictated by the surgeon's manipulationof the virtual tip 905, without relying on the surgeon pushing thecatheter, quasi-blindly, into the patient's body. The magnetic catheterand guidewire assembly 379 (e.g., the magnetic tip can be attracted orrepelled by the electromagnets of the CGCI apparatus 1500) provides theflexibility needed to overcome tortuous paths, since the CGCI apparatus1500 overcomes most, if not all the physical limitations faced by thesurgeon while attempting to manually advance the catheter tip 2 throughthe patient's body.

The guidewire assembly 379 is a tool with a guidewire body 380 and aresponsive tip 2 to be steered around relatively sharp bends so as tonavigate a relatively torturous path through the patient. The responsivetips 2 of both the catheter assembly 375 and the guidewire assembly 379,respectively, include magnetic elements such as permanent magnets. Thetip 2 includes permanent magnets that respond to the external fluxgenerated by the electromagnets as detailed by patent application Ser.No. 10/690,472.

In one embodiment, the responsive tip 2 of the catheter assembly 375 istubular, and the responsive tip 2 of the guidewire assembly 379 is asolid cylinder. The responsive tip 2 of the catheter assembly 375 is adipole with longitudinal polar orientation created by the two ends ofthe magnetic element positioned longitudinally within it. The responsivetip 2 of the guidewire assembly 379 is a dipole with longitudinal polarorientation created by two ends of the magnetic element 2 positionedlongitudinally within it. These longitudinal dipoles allow themanipulation of both responsive tip 2 with the CGCI apparatus 1500, asthe electromagnet assemblies act on the tips 2 and “drag” it in unisonto a desired position as dictated by the operator.

FIG. 4F illustrates a further embodiment of the catheter assembly 375and guidewire assembly 379 to be used with the CGCI apparatus 1500. InFIG. 4F, a catheter assembly 310 is fitted with an additional two (ormore) piezoelectric rings 311, and 312, located as shown. An ultrasonicdetector in combination with the apparatus 1500 provides an additionaldetection modality of the catheter tip whereby an ultrasonic signal isemitted as to excite the two piezoelectric rings and provide a measureof rotation of the catheter tip relative to the North Pole axis of themagnet 2. With the aide of the computer, the CGCI apparatus 1500 iscapable of defining the angle of rotation of the tip 2 and in thepiezoelectric rings 311, 312 can provide additional position informationto define the position, orientation, and rotation of the catheter tip 2relative to the stereotactic framing available from the fiduciarymarkers 700AX and 700BX.

FIG. 4G is an orthographic representation of the catheter assembly 600used for mapping and ablation. The catheter 600, in combination with theCGCI apparatus 1500, allowing the guidance, control, and imaging of thecatheter 600 as it is push/pulled, rotated, or fixed in position. Thecatheter 600 includes an elongated catheter body 376 having a proximalend and an internal longitudinal distal end lumen, where a permanentmagnet 2 (e.g., a magnet formed out of NbFe35 is used as the couplingelements for the CGCI apparatus 1500 in navigating the catheter 600 toits desired designation. The catheter is also fitted with assembly 50(magnetically deployable mechanism) and sensor/antenna head assembly100.

FIG. 4I shows the sensor head assembly 100 and the deployable magneticmechanism 50. FIG. 4I also shows wiring and conduction elements formingthe electrical circuit. A conductor 15 is threaded through a conductor2.1 formed out of suitable polymer and is nested inside permanent magnet2. The permanent magnet 2 is further modified to accommodate anelectrical insulator 2.2 and an electrical ribbon 2.3. The coilelectrical contact 14.1 travels over the ribbon 2.3 to form the “hot”lead (+) of the electrical circuit, while the return path (−) is thepermanent magnet 2. Coil 14 and coil 3 (not shown for clarity) travelsover the electrical ribbon 2.3 and similarly coil 3 travels overelectrical ribbon 2.3 located 180° and electrical contact occurs whencoil contact 3.1 is activated.

FIG. 4J is a cross sectional view of the catheter magnetic device 50whereby, coil 14 is shown with its coil contact 14.1 and electricalribbon 2.3 provide electrical connection between coil 14 and PowerSupply 90 (shown in FIG. 8). The electrical isolation between thepermanent magnet 2 and the electrical ribbon 2.3 is achieved withinsulator 2.2. Further depicted are the conductor carriers (4 each) 2.1and the irrigation tunnel 10.

FIG. 4K shows a top view cross section of the MOSFET sensor head 100(shown in FIG. 2) where the electrical wiring schematic is definedrelative to the antenna 8 and the MOSFET sensor 7.

FIG. 4L is an orthographic depiction of the wiring and electricalcircuit wherein conductor 15 pairs are connected to the antenna 8 andthe MOSFET sensor 7. Electrical ribbon 2.3 with its conductors arethreaded through conductor carrier 2.1. A ground path is provided toground ring 13 to close the electrical circuit.

FIG. 4M provides a view and its cross section of the wiring layout forthe sensor 1600.

FIG. 5 is an orthographic depiction of the internal equivalent circuitof the sensor array. In one embodiment, there are eight MOSFET sensorson the ablation and mapping apparatus 600.

The MOSFET potential sensing device is a junction field effecttransistor that allows a current to flow which is proportional to anelectric field, basically emulating a voltage-controlled resistor. Themodule 100 includes a resistor. The resistor RD 17, is a linear resistorthat models the ohmic resistance of source. The charge storage ismodeled by two non-linear depletion layer capacitors, CGD 23 and CGS 24,and junction capacitors CBD 25, CGD 23, and CBS 19. The P-N junctionsbetween the gate and source and gate and drain terminals are modeled bytwo parasitic diodes, VGD 22, and VGS 21. Gate 1 of the MOSFET sensortip 28 is item 27 and gate 2 of the MOSFET sensor assembly 100 is item26. Gate 1 with reference designator 27 at the sensor tip S(n) (n=1, 2,3, . . . 8) is a relatively high impedance, insulated semiconductorstructure. The device 100 behaves as voltage-controlled resistor. Thepotential between the gate structure 26, 27 and the drain-sourcestructure (RS 18, RD 17) semiconductor substrate defines thetransconductance of the output connections 16.

By connecting the drain-source 17, 18 structure to the sensor body 100,the potential reference for measurement is established. This referenceis configured as a ring 13 along with the catheter body as shown. Themeasurement process of probe 100 is set to a zero voltage as thedrain-source 17, 18 structure, the sensor's gate junction 27 assumes thetissue potential with a relatively small charging current flowing intothe net parallel sum of the junction capacitors, CBD 25, CGD 23, and CGS19. The drain-source 17, 18 voltages is then applied gradually to thedevice charging these capacitors from the outside power source, thereby“nulling” the current needed to form the gate so as to obtain theoperating potential (about 6VDC). The sensing procedure is relativelynoninvasive to the cell as well as to the potential level and currentdrain of the probe 100 upon the cardiac tissue. Gate 2, item 27 providesa biasing input so as to provide a continuous active mode for the probe100. This input is also used for self-calibration of the probe 100.

FIGS. 6, 6A, and 6B are isometric representations of the actuatingmechanism of the magnetically-deployable ablation catheter 50 includingthe coil 3 and its counterpart coil 14 traveling axially on thepermanent magnet 2 (NbFe35). In one embodiment, coil 3 and itscounterpart coil 14 travel axially inside the permanent magnet 2. Byapplying a current, the coil moves toward or opposite to the N-S tips ofthe magnet Z. The magnitude of the coil currents define the position ofthe sensing head 100.

The ablation magnetic assembly 50 includes a 10 mm long and 3.8 mmdiameter NbFe permanent magnet (item 2) and the coils 3 and 14. In oneembodiment, the coils 3 and 14 carry an equivalent current of 200ampere-turns maximum. The coils experience force along the “x” axis. Themagnetic field strength is about 1.2 tesla at the tips. The forces onthe coils range from approximately 0 to ±35 gram-force at approximately100 mA current. Controlling the coil current magnitude and polarity setsthe desired tool positions (states 201, 202, and 203). The fieldintensity along the axis in the permanent magnet 2, is charted by FIG.6A. The travel and force (gram-force) of the assembly 50, along the axis“x” is shown by FIG. 6B.

The ablation sensor head 100 (including the MOSFET sensors 7 and RFantennas 8) travels along the “x” axis to form the measurements path, byproviding an axial travel and opening the manifold to provide:activation state measurement and calibration 200, deployable statesensor head at intermediary state 202, and fully open state 203. Themechanical opening of the sensor head 100, to form various spatialpositions (201, 202, and 203) allowing the apparatus to acquire thedesired measurements on the same region during at least one or more QRScomplex activation sequences and record the data points for relativelyhigh fidelity measurements and error analysis techniques. The use of amagnetically-deployable mechanism to form the position during one ormore QRS complex cycles further allows the apparatus to locate theelectrical wavefront characteristics, so as to determine the geometry ofthe wavefront spreading through the myocardium.

A three-state measurement in the same region while detecting theelectrical activity of the heart improves the measurements where signalquality is poor and provides more data points for construction of theisopotential lines. The error generated due to the abrupt change inpotential is further reduced by the use of the deployable states. Thedeployable state positions allow the apparatus to acquire local featuresof the wavefront such as conduction velocity, potential gradient and/orbreakthrough. A neighborhood of a relatively larger area during theactivation sequence further provides for stability of the acquiredmeasurement and the establishing of statistical significance of thewavefront event recording.

FIG. 7 is a cross section view of the RF antenna 8 used in the ablationmapping apparatus. In one embodiment, there are eight antennas spacedaround the sensor semispherical head 9. The antenna 8, serves twofunctions: it is an electrode that measures the tissue impedance (Z)between the antennas, and it is also serving as the RF ablation tool(the radiator).

The antennas 8 typically should not interfere with the measurements byinjecting or draining the surface potentials 46. The functionalrequirements of the ablation and mapping probe is first to be conductiveduring the impedance tests (Z) 62, and the RF ablation, while theantennas 8 should in a relatively high-impedance state during the ECGmapping 60. In one embodiment, the antennas 8 are formed using, from Njunction 68, and P junction 69, semiconductor (N-P junction).

The operational characteristics of the RF antennas 8 is such that duringthe relatively sensitive ECG potential tests where the controller 1600activates the S₁ MOSFET through S₈ sensor (MOSFETS) the silver coating70 of the antenna 8 is set in a reverse-biased mode. In the reversebiased mode (acting as a diode) leakage current is small (e.g., <1 μA).During the test mode, the tissue is interfaced with the antenna as anelectrode where the junction is set in a forward-biased mode, to conductthe measuring current.

During the RF ablation mode 65, the antennas are set in dual modes ofconduction 62 and radiation 63. There is a conductive path to the tissuethrough the forward biased P-N junction while applying the RF voltage,while the antenna also radiates 63. The arrangement of the antennas 8are set in pairs so that the antennas receive P-N and N-P semiconductorlayers, thus conduction symmetry is maintained. In one embodiment, theP-N layers are shaped around the edges where the conductive part of theantenna 8 meets the insulating case 67, to reduce uneven spot-heating.(The flow effects lesion formation during RF cardiac catheter ablationas the lesion dimensions and tissue heating are dependent not only ontemperature but on other secondary conditions such as heat sinking ofblood flow and impedance value of the tissues).

The antennas 8, radiate 63, about 6 W of RF power each and totalradiating power 63 is approximately 48 W maximum.

The Figure includes the ion flow of measurements performed by thecardiac potential sensors 7 using an isolated MOSFET gate and wiring busnested by the arm 6 which carries the conductors 15 feeds by the powersupply 89.

FIG. 8 is an orthographic depiction of the mapping and ablation catheter600 whereby power supply 94 is provided to the sensor 7 for measuringthe electric potential on the interior cardiac surface, V_(n) 105 whichis a data set electric potential value V_(i) at time T_(i) forming aspatio-temporal manifold 704 (V_(i), T_(i), X_(i), Y_(i), Z_(i)) andcalibration points 700AX and 700BX forming an electric map over the 704grid (manifold). Amplifier 107 transmits a signal measured by the Sensor7 to the data interpolation unit 205 which correlates the space temporalelectric value anatomy on the map (s) which is generated and updated bythe wavefront algorithm (e.g., using the Poynting Energy Vector PEV 49).In one embodiment, there are eight antenna arms 8 spaced around thecentral magnetic head 100, which are controlled so as to form at leastthree spatial states 201, 202, and 203 forming different aperture sizes.The antennas items 8 work during RF ablation in dual modes of conductionand radiation. The conductive path to the tissue through the forwardbiased P-N junction 68 and 69 during RF (300 kHz-1 MHz) voltageapplication 103 (performed by Amp 107 and RF generator 94). Antenna 8also radiates in pairs (4 sets) where the antenna receive P-N and N-Psemiconductor layers, thus conduction symmetry is maintained.Conductivity measurements and impedance values (Z_(n)) 104 are displayedso as to control the ablative energy. In one embodiment, the value ofradiative energy is 6 W of RF power for each antenna with a total energyof approx. 48 W maximum.

During ablation the system 1600 generates RF energy which producesrelatively small, homogeneous, necrotic lesions approximately 5-7 mm indiameter and 3-5 mm in depth. The system 1600 with its mapping andablation catheter 600 is fitted with an irrigation tunnel 10 whichsprays a saline water over the antennas to allow the ablation system tocontrol the energy delivery and rapidly curtail energy delivery forimpedance Z_(n) (104) rise. The saline cools the antennas 8 whichminimizes impedance rises and provides for creation of larger and deeperlesions. In one embodiment, the apparatus 1600 and its MDAMC computer 91is provided with look-up-tables so as to afford a predetermined ablationgeometry formation as a function of multiple parameters affecting thelesion geometry.

In one embodiment, the system 1600 is configured to target the slowerpathway in AVNRT (the inferior atrionodal input to the atrioventricular(AV) node serves as the anterograde limb (the slow pathway). In the caseof WPW (Wolff-Parkinson White Syndrome), the system 1600 is configuredto ablate the accessory pathway which carries the WPW syndrome. In casessuch as atrial flutter due to a large reentrant circuit in the rightatrium a linear lesion of this isthmus cures this form of atrialflutter.

The ability of the ablation system 1600 to form a predefined lesiongeometry is provided by the antenna 8 construction P-N, N-P doping andthe ability of the generator 204 to vary the frequency (Fq) 106 andphase (Fα) 102 so as to afford a precision delivery of energy whichforms the lesion.

In one embodiment, the system 1600 maps the breakthrough and potentialwhile maintaining contact with the myocardium (Z_(n)), tissuedesecration created by the RF energy (500 kHz) which causes a thermalinjury such as desiccation necrosis. RF energy delivered by the antennas8 located on the ablation head assembly 100 causes the resistive heatingof the predefined geometry (linear, section circumference zig zag, etc.)of the tissue in contact with the antenna 8. Cooling the radiatingantennas 8 is performed by the irrigation tunnel 10. In one embodiment,temperature is maintained at approx. 50° C.

FIGS. 9 and 9A show the ablation and mapping catheter 600 as it isintroduced precutaineously into the heart chambers and sequentiallyrecord the endocardial electrograms for correlating local electrogramsto cardiac anatomy. In one embodiment, the catheter is advanced by theuse of magnetic circuits which are capable of generating a magneticfield strength and gradient field to push/pull and bend/rotate thedistal end of the catheter 600 and as detailed by Shachar U.S. patentapplication Ser. No. 10/690,472 titled “System and Method for RadarAssisted Catheter Guidance and Control” hereby incorporated byreference. The catheter 600 is navigated and controlled locally with theaid of fluoroscopy and by the radar as it is detailed by the ensuingdrawings and its accompanying descriptions.

In one embodiment, the catheter 600 is manually advanced into the heartchambers and sequentially recorded the endocardial electrograms, againusing the radar and fiduciary markers for local definition of the site,while advancing the performing the mapping and ablation procedure.

FIG. 9 shows the catheter 600 as it is advanced through the heartchambers 390. FIG. 9A shows the catheter 600 in various deployablestates. In one embodiment, during measurement, the manifold holding thesensor array 8 in the catheter 600, expands from a closed position state201 to a deployable open state [umbrella]. At various open geometrystates, sensor array 8 samples electrical potentials to create a set ofdata points. In one embodiment, the catheter in the deployable stateforms a circular shape as the manifold expands to form various opengeometry states. The intermediary open state 202 indicates an enlargedcircumference and the fully deployable open state 203 represents thesensor array 8 in its maximum spatial coverage.

The intracardiac mapping is performed by measuring the electricalpotential as it moves from state 201 through the state 202 and finallythrough the open state 203. The data is provided to the computer andprocessing functional unit 1600 which controls the procedures.

FIG. 9B shows the endocardial electrogram map 54 resulting fromsequential measurements of electrical potential detected by the sensorarray 100 (including the MOSFET sensor 7 and antenna array 8) in thecatheter 600 at various open geometry states 201, 202, 203. Theconductivity data collected sensor array 8 is processed and graphicallyrepresented using the control display 93 and the E-cardiac display 92.In one embodiment, the conductivity data collected by sensor array 8 isdisplayed in a contour map 49.1 as depicted in FIG. 3, which alsodisplays a contour map 54.1 of the ECG data, and a vector map 53.1 ofthe Energy and E Vector data. In one embodiment, contour map 49.1 of theconductivity data also graphically displays a previous ablation site9004 from created from stored data generated from a previous ablationprocedure. Previous ablation site 9004 represents an area of highimpedance. In one embodiment, the location of previous ablation site9004 is verified using the new data collected from sensor array 8 beforeprevious ablation site 9004 is displayed in contour map 49.1.

FIG. 9B further depicts the fiduciary marker 700A1, 700A2, and 700B1 asshown on the dimensional grid providing the numerical x-y-z coordinateset for the catheter electrical, impedance, measurement performed usingthe catheter 600. Anatomical markers 390.1, 390.2, and 390.3 are notedon the grid and recorded as to their dimensional as well as clinicalsignificance during the travel log of the ablation and mapping catheter600. Further detail of the procedure by which catheter 600 acquires theelectrical and conductivity data relative to dimensional as well asanatomical marker are described in FIG. 10.

The system 1600 with its mapping and ablation catheter 600 performs thetasks of mapping using the sensor array 100 as follows: calibration andposition definition using radar 1000, cardiac morphology and geometrysynchronization with images generated by x-ray fluoroscopy or MRI etc isestablished. (Synchronization methodology is provided by radar 1000 andfiduciary markers 700AX and as it is detailed by FIGS. 11 and 11A).

Data obtained from sensor array of catheter 600 is processed and itsgeometry and dimensional attributes are defined as to its physiologicalreference. Data of maps are stored relative to its fiduciary markers, soit can be retrieved and used during the ablation sequence.

The ablation catheter is then directed to its desired site. Thewavefront characteristics are established using the Poynting EnergyVector (PEV) 49 and the reconstruction of the potentials and maps of thewavefront is established as detailed as shown in FIG. 10 and itsmathematical algorithm in connection with FIG. 3.

The computer-generated maps and model analysis of the endocardium isperiodically updated as the catheter head assembly 100 with its sensorarray 7 is moved along the cardiac chamber.

The electrogram is synthetically constructed upon the x-ray fluoroscopyimage which is pixelized and voxelized so as to allow the mapping of thewavefront characteristics as it is dimensionally, as well as,graphically layered over the heart morphology. The geometrization of theelectrical potential and its maps is further detailed by FIGS. 8 and 9.

FIG. 10 is an isometric representation of the image capture techniqueused by the system 1600 in identifying the position and coordinate ofthe catheter 600 as it moves through the heart chambers. The electricpotential measurements taken by the catheter 600 are tracked and gatedby the radar 1000 to allow determination of the 3D position coordinatesof the catheter tip in real time. The radar and its fiduciary markersprovide for the detail dimensional travel map of the catheter as it issampling (S/H) the electric potential. The system 1600 reconstructs themaps on a grid formed as a 2D pixelized layout superimposed over thereconstructed myocardium chambers or as a voxel 3D vector position. Thedetails of such scheme are outlined by FIGS. 11, 11A, 12, and 12A.

The catheter 600 position is determined by the radar 1000, whichmaintains a position and orientation above the patient. In oneembodiment, the radar 1000 is set approx. 1 meter from the fiduciarymarkers placed on or in the patient's body so that phase and range datais defined and beam compensation can be determined. To obtain thecalibration points so as to track the moving catheter (range ofmovements is between 0.2-2 Hz band). The volume integrated, i.e., thecardio chamber (s) is denoted by voxels. Temporal filter such as an FFTdenoted by FIG. 11, item 1103, allows the rendering of the signalreceived from the catheter 600 to be position bound to the originalcalibrating points.

In one embodiment, the ablation and mapping catheter 600electromechanical characteristics are; the catheter in closed state 201is 5.12 mm in diameter. The sensor tip movement is between 1-10 mmdiameter (fully opened state 203), the axial movement is 2 mm and thesensor head 100 tool force is 0 to ±35 gram, total radial movement along360° is 24 position (15° along the circumference), the ablation power is50 WRF with ablation cut size of 1-2.5 mm. The ablation tool force is0-35 grams. Eight antennas 8 are spaced along the protective dome 9which carry eight MOSFET sensors 7.

When the catheter 600 is used while employing the CGCI apparatus, asnoted by U.S. patent application Ser. No. 10/690,472, the catheter 600exerts a force control of 0 to ±37 grams with torque control of 0 to ±35grams.

The catheter 600 is detected by the radar 1000 and it is placed over themanifold 704 which is placed over the imaging x-ray fluoroscopy 702while gated by the fiduciary markers 700AX, the normalization procedureperformed by the system computer 91 (orthogonal basis) allows thecalibration of the catheter tip 2 relative to the fiduciary markers700AX located on the patient 390 body forming the stereotactic frameused in forming the manifold 704. Navigating the catheter 600 is trackedby denoting the radar initial position as 600 x radar (t), thetime-varying position of the catheter tip 2, while the fiduciary markers700AX is denoted by X₀ (t) and is determined as voxel o. The other fixedtargets are for example the fiduciary markers mounted on the operatingtable 700BX (fixed targets).

The ranges of the fiduciary markers 700AX and 700BX are denoted by X_(i)(t); i=1, 2, . . . n. The fiduciary markers are passive devices emittinga radar cross section (RCS) suitable for formation of the manifold 704,while traveling for example through the coronary sinus, the system 1600record each sign post which facilitates the formation of anatomical signposts while forming the map (cardio chamber geometry). The sign postsare anatomical in nature and assist in realistic rendering of thesynthetically-generated virtual heart surface. Electric potential datasets of ordered pairs <E_(n), T_(i)> are recorded and are placed on thedimensional grid (manifold 704) generated by the radar 1000. The mappingprocess is data set of <E_(i), T_(i)>60, a corresponding <M_(i),T_(i)>61 and an impedance value <Z_(i), T_(i)>62, data points are gatedto the dimensional grid 704 (the manifold with its fiduciary markers700AX and permanent reference markers 700BX). The radar 1000 generates adimensional 3D travel map which is kept for further use. Cardiac motionand pulmonary outputs are gated by the fiduciary marker calibration andbody electrogram (ECG). QRS complex cycle is employed in correctingalgorithms. The data points <E_(i), M_(i), and T_(i)> are correlated tothe grid 704 while correction of position as well as calibration isperformed in background mod.

The sensor array 100 with its measuring devices (as detailed by FIGS. 2and 5) used by the mapping and ablation catheter is designed to enhancethe acquisition of temporal/electric potential measurements within thecardiac chambers while correlating space temporal data reconstructedfrom 3D fields. The system 1600 further provides data sets from andaround the ablation area tissue surface. In one embodiment, data of thespread of excitation and the magnitude of the time-varying electricpotential in 3D is obtained by the use of the sensors 7, which aregalvanically isolated from the tissue to be measured.

The sensor 7 further provides for substantial increase of sinal to noiseradio due to an device-signal-amplification. The catheter assembly 600is introduced percutaineously into the heart chambers, by the CGCIapparatus (see U.S. patent application Ser. No. 10/690,472 incorporatedherein its entirety).

The catheter tip 2 and the sensor head 100 is initially set at closedposition (state 201). The catheter 600 is then activated so as toenergize coil 3 and coil 14, deploying the sensor 7 array 100 to itsfully open position (state 203).

The sensor array 7 is used to provide readings at two or three positions(201, 202, 203) with incremental radii sensor 7 (S₁-S₈). The electricpotential (with its temporal as well as dimensional elements) isprovided to the ECG data interpolation unit 205, based on the datafidelity the system controller 91 instructs the sensor head assembly 100to move by deploying the magnetic apparatus 50 so as to formmeasurements along the different states 201, 202, and 203. The axialmovement of magnetic assembly 50 with its two electromagnetic coilstravels along the guide rail 4.

The axial movement of coils 3 and 14 displaces the arm 6 (which holdsthe sensors 7 and the RF antenna 8) so as to form an “umbrella” withmultiple states (201, 202, and 203). The action of the magnetic assembly50 is the result of the solenoid action generated by polarity andmagnitude of the coils 3 and 14 relative to the permanent magnet 2.

In one embodiment, the CGCI apparatus 1500 is used to generate amagnetic field parallel to the axis of the catheter 600 permanent magnet2, holding the catheter tip in position (desired position) and the CGCIapparatus produces a gradient in this aligned field without changing itsholding direction (the precision of fixing the catheter 600 in itslocation allows repeated measurements.

The catheter 600 and its associated controller as shown in FIG. 2 can beused to measure the activation time (t_(i)) by sampling the location(site) repeatedly, generating multiple elements of (E_(i)-T_(i)) pairsto characterize the geometrical layout of electric potential on 2D(pixels) or 3D (voxels) maps. Such maps are generated using the electricheart vector (EHV), the correlated magnetic dipole (MHV) as well asimpedance values (Z) and superimposition of such maps over thesynthetically generated endocardium.

In one embodiment, the endocardium chamber geometry is modeled by analgorithm such as a simplified FEA, which models the wavefront PoyntingEnergy Vector 49, hence identifying sites of ectopic activation.Automatic activation geometry is further located by the radar signalsforming the grid 704 to locate the path of anisotropy due to transmuralfiber rotation, that were reconstructed with spatial resultant of >0.5mm. The data points received from the catheter 600 with its sensors 7,electronically interact with the cardiac cells and such interactions arecollected as measured data. The energy wavefront Poynting Energy Vector(PEV) 49 is used in solving the non-linear parabolic partialdifferential equation. The transmembranes potential typically behavessimilar to a cellular automation. Hence, the use of the HausdorfNeighborhood theorem is an appropriate description of theelectrophysiological avalanche. The maps generated by the algorithmdescribed as the Poynting Energy Vector (PEV) 49 can be reconstructed asimages using color for differentiating regions based on densitydistribution or a mash technique of geodesic line representing theelectric potential (on a grid with time domain) as an elevation abovethe ground potential (zero), and/or as abnormal low voltage representsscar tissue which might express the underlying arrhythmia.

FIG. 11 is a block diagram of a radar system 1000 used in one embodimentof the CGCI apparatus 1500. The radar 1000 shown in FIG. 11 includes aphased-array radar module 1100 having transmit/receive antenna elementsand a Radio Frequency (RF) module 1150. The radar system 1000 includesan amplifier 1101, an A/D converter 1102, a Fast Fourier Transformmodule 1103, and a microcontroller 1105. The apparatus further includesa memory module in the form of RAM 1112, and a look-up table in the formof a ROM 1111.

One embodiment includes a voice messaging and alarm module 1110, a setof control switches 1109, and a display 1108. The data generated by theradar system 1000 is provided to the GCI apparatus 501 viacommunications port 1113.

The radar system 1000 includes a phased-array and uses Microwave Imagingvia Space-Time (MIST) beam-forming for detecting the catheter tip 2. Anantenna, or an array of antennas, is brought relatively near the body ofthe patient and an ultra wideband (UWB) signal is transmittedsequentially from each antenna. The reflected backscattered signals thatare received as radar echoes are passed through a space-time beam-formerof the radar unit which is designed to image the energy of thebackscattered signal as a function of location. The beam-former focusesspatially on the backscattered signals so as to discriminate from thebackground clutter and noise while compensating for frequency-dependentpropagation effects. The contrast between the dielectric properties ofnormal tissue and the catheter tip 2 in the regions of interest providessufficient backscatter energy levels in the image to distinguish normaltissue from the catheter tip 2, affording detection and discern ability.In one embodiment, a data-adaptive algorithm is used in removingartifacts in the received signal due to backscatter from the body tissueinterface (e.g., the skin layer). One or more look-up tables containingthe known dielectric constants of the catheter tip contrasted againstthe background dielectric information relative to the biological tissuecan be used to identify features in the radar image.

The physical basis for microwave detection of the catheter tip 2 in thebiological tissue is based on the contrast in the dielectric propertiesof body tissue versus the signature of the catheter tip 2. The contrastof the dielectric values of biological tissue versus that of thecatheter tip 2 is amplified, filtered and measured.

A typical summary of dielectric properties in living tissues for medicalimaging in the range of 10 Hz to 20 GHz and parametric models for thedielectric spectrum of tissues are configured to an (ε′) of 5-60 andelectrical conductivity (σ) of 0.065-1.6 Simens/m (S/m) the relativecomplex permittivity, ε_(r), of a material is expressed as:

ε_(r)=ε′+ε″)

ε′=ε/ε₀

ε″=σ/ε₀ω

Where ε is the permittivity, ε₀ is the permittivity of freespace=8.854e-12 Farads/m, ε″ is the relative dielectric loss factor, andω is the angular frequency.

The return waveform from the radar 1000 is provided to a computer usinga software such as MATLAB. A target such as the catheter tip 2 issampled with a transmitted pulse of approx. 100 ps in durationcontaining frequency from 400 Hz to 5 GHz with a range of approx. 1meter in air (the range of the electromagnetic coil location). The radaremits a pulse every 250 ms (4 MHz). The return signals are sampled andintegrated together to form the return waveform as measured on circuit1000. A specific window of data of the radar interaction with the target2 is obtained and a Fast Fourier Transform (FFT) of the window of datais taken to produce the frequency response of the target 958:

${X(k)} = {\sum\limits_{j = 1}^{N}{{x(j)}W_{N}^{{({j - 1})}{({k - 1})}}}}$

and by taking a Fast Fourier Transform (FFT) 1103 it is possible toidentify the differences between metal 2, or human tissues, etc. Thesynthetic aperture radar 1117 (SAR) aids in the signal processing bymaking the antenna seem like it is bigger than it really is, hence,allowing more data to be collected from the area to be imaged.

The radar can use time-domain focusing techniques, wherein thepropagation distance is given:

d=2√{square root over ((x)²+(z)²)}{square root over ((x)²+(z)²)}

and alternatively a propagation time computed given by:

$t = \frac{2\sqrt{(x)^{2} + (z)^{2}}}{v}$

In one embodiment, target identification and matching is performed bycharacterizing the target waveform of the catheter tip 2 into a singlevector. The dot product is taken from the identification vector and thedata whereby, perfectly aligned data and ID results in a dot product of1, and data perpendicular to the ID (2) is resulting in dot productequal to zero. The radar controller 1105 converts the results to apercent match (dielectric value, conductivity measure) of the data ofthe identification vector.

The catheter tip 2 has a microwave scattering cross-section that isdifferent relative to biological tissue of comparable size. Thedifference in scattering cross-section is indicated by the differentback-scatter energy registered by the receiver, and processed so as toafford a pictorial representation on a monitor 325 with a contrastbetween the two mediums. The pictorial view of the catheter tip 2generated by the radar system 1000 can be superimposed over the X-rayfluoroscopy image 702 and its coordinate data set linked to the GCIcontroller 501 for use as a position coordinate by the servo feedbackloop. In one embodiment, microwave imaging via space-time (MIST)beam-forming is used for detecting backscattered energy from thecatheter tip 2 while the background is biological tissue.

In one embodiment, a data set <E_(i)T_(i)> and <x; y; z> positioncoordinates are used with the ablation and mapping apparatus 1600 informing the maps as shown in FIG. 10.

The radar system 1000 detects the presence and location of variousmicrowave scatters, such as the catheter tip 2, embedded in biologicaltissue 390. The space-time beam-former assumes that each antenna in anarray transmits a low-power ultra-wideband (UWB) signal into thebiological tissue. The UWB signal can be generated physically as atime-domain impulse 960 or synthetically 1117 by using a swept frequencyinput. In one embodiment, the radar system 1000 uses a beam-former thatfocuses the backscattered signals of the catheter tip 2 so as todiscriminate against clutter used by the heterogeneity of normal tissueand noise while compensating for frequency-dependent propagationeffects. The space-time beam-former achieves this spatial focus bytime-shifting the received signals to align the returns from thetargeted location. One embodiment of the phased-array radar 1000 forms aband of finite-impulse response (FIR) filters such as high dielectricdoping in the antenna cavity, forming the reference signal, where thedoping is relative to the device of interest (e.g., catheter tip 2). Thesignals from the antenna channels are summed to produce the beam-formeroutput. A technique such as weights in the FIR filters can be used witha “least-squares fitting” technique, such as Savitzky-Golay SmoothingFilter to provide enhancement of the received signal and to compute itsenergy as a function of the dielectric properties versus the scatteredbackground noise of body tissue, thereby providing a syntheticrepresentation of such a signal. The system can distinguish differencesin energy reflected by biological tissues 390 and the catheter tip 2 anddisplay such energy differences as a function of location andco-ordinates relative to the fiduciary markers 700Ax through 700Bx. Inone embodiment, the radar module 1000 uses an FFT algorithm 1103 whichuses a filtering technique to allow the radar 1000 sensor to discernvarieties of dielectric properties of specific objects known to be usedin a medical procedure, such as a guidewire 379 and/or a catheter 310with piezoelectric ring 311 and 312 so as to afford differentiation ofvarious types of instruments like catheters, guide-wires, electrodes,etc.

FIG. 11A is a graphical representation of the catheter tip 2 embeddedwith one, two or more piezoelectric rings 311 and 312 such asLead-Zirconate-Titanate (PZT) and/or molecularly conjugated polymerssuch as switchable diodes (polyacetylene). The second harmonicsgenerated by the rings 311 and 312 provide an identifiable returnsignature in the second harmonic due to the non-linearity of thematerial. While the fundamental harmonic (e.g., 5 MHz) is transmitted bythe radar, the second harmonic (e.g., 10 MHz) is readily distinguishableby the radar system 1000. This allows the radar system 1000 to discernbetween the catheter tip 2 (which typically has a ferrite such assamarium-cobalt SmCo5, or neodymium-iron-boron, NdFeB) and the PZT rings311 and 312. The ability to distinguish between the signal return fromcatheter tip 2 and the PZT rings 311 and 312, allows the radar system1000 to filter out the background clutter received from the body tissueand to recognize the position and orientation of the rings 311 and 312and the position co-ordinates of the catheter tip 2. The technique ofusing two different dielectric properties and electrical characteristicsof the tip 2 versus the PZT 311 and 312 provides the catheter tip 2 witha radar signature that can be recognized by the radar system 1000.

FIG. 11B further illustrates how the radar system 1000 with its transmitand receive antennas is used to detect the position co-ordinates andorientation of catheter tip 2 relative to its two PZT rings 311 and 312.A geometrical manipulation is employed by the radar system 1000 and itsassociated FFT filter 1103 by the resident microcontroller 1105. Asshown in FIGS. 4D, 4E, 4F, a catheter-like device is provided with amagnetically-responsive tip 2. In one embodiment, the tip 2 includes apermanent magnet. The polarity of the permanent magnet is marked by twoPZT rings where the north pole is indicated by a PZT ring 312 and thedistal end of the ferrite where the semi-flexible section 310 of thecatheter 376 is marked with the additional PZT ring 311, also markingthe south pole of the ferrite.

In one embodiment, the ferrite 2 in the catheter tip is used by theablation and mapping catheter 600 as described by FIG. 4 and itsaccompanying descriptions.

The radar system 1000 transmits a burst of energy that illuminates theferrite catheter tip 2. The return signal from the catheter tip 2 isreceived by the radar and its position is registered by observing thetime of flight of the energy, thereby determining the location of thecatheter tip 2 as position co-ordinates in a three-dimensional space. Byemploying the two PZT rings 311 and 312, the radar detector 1000 is alsocapable of discerning the location of the tip 2 relative to the two PZTrings so as to afford a measurement of PZT ring 312 relative to thesecond piezoelectric ring 311 with reference to the positionco-ordinates of catheter tip 2. The radar detector 1000 can discern thereturn signal from PZT rings 311 and 312 due to the non-linearcharacteristic of PZT material that generates a second harmonic relativeto the incident wave. By comparing the strength of the fundamentalfrequency and the second harmonic, the radar system 1000 is able todiscern the position and orientation of the two PZT rings relative tothe ferrite 2, thereby providing position and orientation of thecatheter tip 2.

FIG. 11B illustrates the technique of measuring the position andorientation of the catheter tip 2 by the use of the radar detector 1000and using the fiduciary markers 700AX and 700BX to form a frame ofreference for the catheter dynamics such as movement relative to theframe of reference. As shown in FIGS. 11A and 11B the fiduciary markers700AX and 700BX form a manifold 701. The locations of the markers 700AXand 700BX are measured by the radar system 1000.

In one embodiment, the markers are electrically passive and can be madefrom a polymer or PZT material to allow the radar antenna to receive asignal return which is discernable. Criteria such as the conductivity ofa substance such as catheter tip 2 relates at least in part to how muchthe radar signal is attenuated for a given depth (e.g., the higher theconductivity the higher the loss for a constant depth). An averageconductivity of 1S/m at 1 GHz signal would penetrate the human body 390approximately 1.8 cm.

The dielectric constant of all targets is typically less than 5 (e.g.,cotton(1.35), Nylon 5, etc.). The conductivity of metals is relativelylarge, and relatively small for most dielectrics (with Nylon on theorder 1e-3 and that of cotton and rayon being saturated by that ofwater, blood and tissue). The relative permittivity of the targets willbe in the order of 2-3 orders of magnitude lower than that of thesurrounding tissue, and the conductivity of the metals will be 6-7orders of magnitude greater than that of the surrounding tissue.

The dielectric properties as well as the conductivity measure of thetarget catheter tip 2 and/or its directional markers PZT rings 311 and312 allow the radar 1000 to discern the target out of the surroundingclutter (body tissue 390) and perform the task of position definition 2within the referential frame of fiduciary markers 700AX and 700BX.

In one embodiment, the return waveform is recorded for a static(clutter) environment, and then a target is inserted into theenvironment and once the clutter is subtracted from the return waveformthe radar 1000 processes a target response (clutter is a general termreferring to anything the radar will interact with that is not a desiredtarget). In one embodiment, the data is processed and defined in termsof a machine language as model for the CGCI controller 501 and is usedby the controller to close the servo loop. In one embodiment, the datagenerated by the radar 1000 is used for mapping and ablation system 1600and its computer 91 to form the grid/manifold 704 so as to enable thedimensional placement of the <E_(i)T_(i)> pairs <M_(i)T_(i)> pairs. Thedata 60 and 61 are then used by the imaging graphic generator 200 toform the vectoral electrocardiograph maps.

FIGS. 12 and 12A show an image displayed on the monitor 325. Thecineoangiographic image 702 of an arterial tree is shown with areconstructed radar signature of the catheter tip 2. The image 702contains a numerical grid defined and calculated by the radar 1000 and adata set of coordinate or vector representation of catheter positionwhere the Actual Position (AP) is displayed. A similar data set ofcatheter position 2 is fed to the CGCI controller 501 or to the ablationcomputer 91 for the purpose of closing the loop of the servo controlsystem of the CGCI apparatus 1500 and for definition of the dimensionalgrid for ablation. A graphic depiction of the catheter tip 2 is shown inFIG. 12 where the monitor 325 displays the stereotactic frame formed bythe fiduciary markers 700AX and 700BX obtained from the radar signature1000. The catheter tip 2 is shown in the approximate cube formed by thefiduciary markers 700AX and 700BX. The ensemble of position datarelative to coordinates, is formed as dynamic manifold 704. The manifold704 is used for a processing synchronization of the catheter tipposition (AP) relative to the stereotactic frame 701. The process ofsynchronization is gated in the time domain with the aid of an EKGelectrocardiogram 502, whereby the controller 501, internal clock issynchronized with the EKG QRS complex so as to provide a Wiggers'diagram. Synchronization allows the CGCI controller 501 to gate thedimensional data and coordinate set of fiduciary markers so as to movein unison with the beating heart. The technique noted by ImageSynchronization 701 allows the ablation catheter 600 and its computer 91to update the electrocardiograph maps on a real time basis henceenabling the system 1600 to form an accurate view of the mapping andablation and therefore reduce the use of x-radiation.

Synchronization of the image of the catheter tip 2 or guidewire 379,captured by the radar system 1000, is superimposed onto the fiduciarymarkers which are represented digitally and are linked dynamically withthe image 702. This is done so as to create a combined manifold 704,which is superimposed onto the fluoroscopic image 702, and moves inunison with the area of interest relative to the anatomy in question.For example, the beating heart and its cardio-output; the pulmonaryexpansion and contraction, or spasm of the patient 390, all these aredynamically captured and linked together so as to achieve a substantialmotion in unison between the catheter's tip and the body organ inquestion.

Synchronization 701 of the catheter tip 2 with its referential markers700AX and 700BX allows for dynamically calibrating the relative positionand accurately gating the cineographic image (or ultrasonic) with thebeating heart. Further, the CGCI 1500 and the ablation/mapping catheter1600 can be used to capture the data set-manifold 704 in the time domainof the patient 390 EKG signal. The CGCI controller 501 and/or theablation system 1600 can display and control the movement of thecatheter tip 2 in unison with the beating heart. Synchronization by theuse of fiduciary markers 700AX and 700BX captured by the catheter tip 2,using the data set 704, and superimposing it over the cineographic image702 and gating it based on EKG signal from the patient's body 390,allows the position data to be linked to the controller 501/91 to closethe servo loop and to provide the dimensional grid for forming theelectrical maps.

The CGCI controller 501/91 can perform the data synchronization withoutthe active use of x-ray imagery since data of catheter position isprovided independently by the radar signal 1000.

The invention is not limited only to the examples described above. Otherembodiments and variations will be apparent to one of ordinary skill inthat art upon reading the above disclosure. Thus, the invention islimited only by the claims.

1. A catheterization method, comprising: guiding a distal end of acatheter to a desired region of tissue; spreading sensor arms of saidcatheter; establishing contact between said sensor arms and the regionof tissue; sensing a position of said sensor arms; measuring activationpotential data using sensors provided to said sensor arms; measuringimpedance data of tissue between said sensor arms using contactsprovided to said sensor arms; and displaying a map of activationpotential and impedance of said region of tissue.
 2. The method of claim1, further comprising using said activation potential data and saidimpedance data in a calculation to predict an RF ablation lesion.
 3. Themethod of claim 2, further comprising creating an RF ablation lesion. 4.The method of claim 1, wherein said sensors comprise MOSFET sensors. 5.The method of claim 1, wherein said contacts comprise PN junctions. 6.The method of claim 1, wherein said contacts comprise alternating PNjunctions.
 7. The method of claim 1, further comprising calculating anangle between an E vector and an energy vector in said region of tissue.8. The method of claim 7, further comprising identifying anomalies inactivation vector spreads where an angle between said E vector and saidenergy vector exceeds a threshold.
 9. The method of claim 1, whereinsaid position of said sensor arms is measured using radar.
 10. Themethod of claim 1, wherein said position of said sensor arms is measuredusing X-rays.
 11. The method of claim 1, further comprising: calculatinga desired direction of movement for said distal end; computing amagnetic field needed to produce said movement; controlling a pluralityof electric currents and pole positions to produce said magnetic field;and measuring a location of said distal end.
 12. The method of claim 1,further comprising controlling one or more electromagnets to producesaid magnetic field.
 13. The method of claim 1, further comprisingsimulating a magnetic field before creating said magnetic field.